text: Berthelot independently enunciated a generalization (commonly known as Berthelot's Third Principle, or Principle of Maximum Work), which may be briefly stated as: every pure chemical reaction is accompanied by evolution of heat. Whilst this principle is undoubtedly applicable to the great majority of chemical actions under ordinary conditions, it is subject to numerous exceptions, and cannot therefore be taken (as its authors originally intended) as a secure basis for theoretical reasoning on the connection between thermal effect and chemical affinity. The existence of reactions which are reversible on slight alteration of conditions at once invalidates the principle, for if the action proceeding in one direction evolves heat, it must absorb heat when proceeding in the reverse direction. As the principle was abandoned even by its authors, it is now only of historical importance, although for many years it exerted considerable influence on thermochemical research.
  Thus, to summarize, in 1875 by the French chemist Marcellin Berthelot which stated that chemical reactions will tend to  yield the maximum amount of chemical energy in the form of work as the reaction progresses.
  In 1876, however, through the works of Willard Gibbs and others to follow, the work principle was found to be a particular case of a more general statement:
  The principle of work was a precursor to the development of the thermodynamic concept of free energy.